The present invention relates to I/O controllers and device drivers that may program them. More specifically, the invention relates to a method and apparatus for reducing the disk drive data transfer interrupt service latency penalty.
Before data may be read from, or written to, a computer""s hard drive, a host system must issue a read or write request to the hard drive. In response to such a request, the hard drive in concert with a DMA engine transfers the data to, or from, the host system. The hard drive then issues an interrupt to inform a device driver that the transfer is complete. Because that interrupt is not issued until the end of the data transfer, there is a delay between data transfer completion and device driver notification of that event. That delay, which results from the command overhead inherent in routing the interrupt from the disk drive to the operating system and then to the driver, can be significantxe2x80x94e.g., 10 microseconds for each disk access. Eliminating, or reducing, such an interrupt service latency penalty could significantly enhance a computer""s performance.
Accordingly, there is a need for an apparatus and method that reduces the command overhead associated with the transfer of data between a disk drive and a host system. The present invention provides such an apparatus and method.